Towards a self-consistent non-linear theory of radar auroral backscatter

Robinson, T. R.

doi:10.1016/0021-9169(86)90118-2

Cited by 150 publications

(156 citation statements)

References 18 publications

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“…Examination of STARE beam 0 (azimuth~13°) reveals that l-o-s velocities in a near-meridional direction are~4 times smaller than those measured in beams 3 and 4. Also, the poleward component of velocity, v x , measured by STARE is likely to be underestimated due to soundspeed limiting e ects (Robinson, 1986). Furthermore, the use of l-o-s velocities from multiple beams introduces a temporal o set between each beam's estimated conductance pro®le.…”

Section: Derived Ionospheric Hall Conductancesmentioning

confidence: 99%

Multi-instrument observations of the electric and magnetic field structure of omega bands

et al. 2000

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Abstract. High time resolution data from the CUT-LASS Finland radar during the interval 01:30±03:30 UT on 11 May, 1998, are employed to characterise the ionospheric electric ®eld due to a series of omega bands extending~5°in latitude at a resolution of 45 km in the meridional direction and 50 km in the azimuthal direction. E-region observations from the STARE Norway VHF radar operating at a resolution of 15 km over a comparable region are also incorporated. These data are combined with ground magnetometer observations from several stations. This allows the study of the ionospheric equivalent current signatures and height integrated ionospheric conductances associated with omega bands as they propagate through the ®eld-of-view of the CUTLASS and STARE radars. The high-time resolution and multi-point nature of the observations leads to a re®nement of the previous models of omega band structure. The omega bands observed during this interval have scale sizes~500 km and an eastward propagation velocity~0.75 km s A1 . They occur in the morning sector (~05 MLT), simultaneously with the onset/intensi®ca-tion of a substorm to the west during the recovery phase of a previous substorm in the Scandinavian sector. A possible mechanism for omega band formation and their relationship to the substorm phase is discussed.

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Section: Derived Ionospheric Hall Conductancesmentioning

confidence: 99%

Multi-instrument observations of the electric and magnetic field structure of omega bands

et al. 2000

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“…Type I spectra have a low spectral width and a velocity constrained to be near the local ion-acoustic speed, C s , which typically takes a value of 350±400 ms A1 at 110 km, the velocity threshold for the generation of the two-stream instability (Sudan, 1983;Nielsen and Schlegel, 1983). For high electron¯ow speeds, C s (and hence the Doppler velocity of type I spectra) increases (Robinson, 1986), but in general remains an underestimate of the true drift speed. This is an important consideration for convection studies, producing inaccuracy not only in¯ow speed estimates, but also¯ow direction in the case of bistatic merged vector velocities; type I spectra are often considered to be contamination of HF radar backscatter.…”

Section: Introductionmentioning

confidence: 99%

Initial backscatter occurrence statistics from the CUTLASS HF radars

et al. 1997

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Abstract. A statistical study of the occurrence of ground and ionospheric backscatter within the ®elds-of-view of the CUTLASS HF radars, at an operating frequency of 10 MHz, during the ®rst 20 months of operation has been undertaken. The diurnal variation of the occurrence of backscatter and the range at which such backscatter is observed is found to be highly dependent on seasonal changes of the ionospheric electron density in both the E and F region, determined from ionosonde observations. In general, ionospheric backscatter is observed at far ranges during the local day in winter months and at near ranges during the local night in summer months. The Iceland radar observes more nearrange E region backscatter than the Finland radar as a consequence of its more zonal look-direction. The dependence of the occurrence of backscatter on geomagnetic activity and radar operating frequency are also investigated. The occurrence of ground and ionospheric backscatter is discussed in terms of HF propagation modes and ionospheric electron densities as well as geophysical processes. A brief assessment of the possible impact of solar cycle variations on the observations is made and frequency management is discussed. Such a study, with its focus on the`instrumental' aspect of backscatter occurrence, is essential for a full interpretation of HF coherent radar observations.

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“…More proper (less in-97 tuitive) theoretical explanations have been given in the literature on occasions. At high latitude, one explanation that has been advanced is that anomalous diffusion increases with the amplitude of a structure until it stops growing (Robinson, 1986). A problem with this mechanism, however, is that the diffusion is from the electron drifts and therefore at right angles to the direction needed for diffusion to affect the wave amplitude (St.-Maurice, 1990).…”

Section: Vertical Type I Echoes At Low Latitudesmentioning

confidence: 99%

The influence of non-isothermal electrons and neutral wind structures on the doppler properties of vertical m-size field-aligned irregularities in the low latitude E-region

St.-Maurice¹,

Choudhary²

2007

Rev. Bras. Geof.

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ABSTRACT.Meter size irregularities are routinely studied with radars in the equatorial and low latitude regions. In both instances echoes from the E-region (90 to 120 km altitude) are a common occurrence. The resulting echoes are labeled as so-called Type I or Type II according to their spectral signature. In this paper we show that the phase velocity of Type I echoes increases with decreasing altitude owing to thermal feedback effects taking place in the growth process. We also show that Type II echoes can be influenced by atmospheric neutral winds to the point of revealing the presence of Kelvin-Helmholtz billows, as shown by a recently studied example taken from the Gadanki radar in India.Keywords: equatorial electrojet, plasma waves and instabilities, ionospheric irregularities, low latitude E-region, VHF radar spectra, quasi-periodic echoes, KelvinHelmholtz billows, turbulence.RESUMO. Irregularidades com escala de metros são estudadas rotineiramente com radares nas regiões de baixas latitudes e equatoriais. Em ambos os estudosé comum a ocorrência de ecos da região E (90 a 120 km de altitude). Os ecos resultantes são denominados de Tipo I e Tipo II de acordo com sua assinatura espectral. Neste trabalho nós mostramos que a velocidade de fase dos ecos tipo I aumentaà medida que diminui a altitude devido a efeitos térmicos causados pela própria irregularidade durante seu processo de desenvolvimento. Nós também mostramos que os ecos do Tipo II podem ser influenciados pelos ventos neutros atmosféricos ao ponto de revelar a presença de ondas do tipo Kelvin-Helmholtz, conforme demonstrado em alguns exemplos de estudos recentes realizados com o radar Gadanki naÍndia.Palavras-chave: eletrojato equatorial, ondas de plasma e instabilidades, irregularidades ionosféricas, região E em baixas latitudes, espectros obtidos com radares em VHF, ecos quase-periódicos, ondas do tipo Kelvin-Helmholtz, turbulência.

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Towards a self-consistent non-linear theory of radar auroral backscatter

Cited by 150 publications

References 18 publications

Multi-instrument observations of the electric and magnetic field structure of omega bands

Multi-instrument observations of the electric and magnetic field structure of omega bands

Initial backscatter occurrence statistics from the CUTLASS HF radars

The influence of non-isothermal electrons and neutral wind structures on the doppler properties of vertical m-size field-aligned irregularities in the low latitude E-region

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